Accurate air charge estimation is useful for electronic control of internal combustion engines, in particular to improve operating characteristics and fuel efficiency of engines.
Air enters the cylinders of the engine through an intake manifold. The air charge is defined as the amount of air the engine inducts for each combustion event. The engine may have various sensors, such as an engine speed sensor or manifold pressure sensor, but there is no direct measurement of the air charge for the cylinders. Accurate estimation of air charge is difficult over the wide range of possible engine operating conditions, and if the air charge is not accurately estimated, the air/fuel ratio and engine operation will be sub-optimized.
Hence, improved air charge estimation is useful for improving engine operation and the fuel efficiency of internal combustion engines. There are great environmental and cost benefits from improved fuel efficiency.